Electric circuit for igniting a discharge lamp, and electric component module and discharge lamp incorporating such an electric circuit

ABSTRACT

An electric circuit for igniting a discharge lamp includes a voltage source, and at least one condenser electrically connected to the voltage source. Further, a series chain is provided, electrically connected in parallel with the condenser, of at least one ignition and at least one inductor. A discharge lamp is electrically connected in parallel with the ignition.

The invention relates to an electric circuit for igniting a dischargelamp, comprising a voltage source, at least one first condenserelectrically connected to the voltage source, a series chain,electrically connected in parallel with the first condenser, of at leastone ignition and at least one first inductor, and a discharge lampelectrically connected in parallel with the ignition, which dischargelamp is provided with a discharge vessel. The invention also relates toan electric component module for use in such an electric circuit. Theinvention further relates to a discharge lamp incorporating such anelectric circuit.

The awareness of the need for power conservation is becoming asignificant factor both for purchasers as well as for lighting equipmentmanufacturers. The feature of a higher efficacy of a burner of HighPressure Sodium (HPS) lamps while retaining at least the same lightintensity results in a lower power consumption, which creates clearbenefits for the purchaser. A method known in the art to achieve a lowerpower consumption consists in lowering the burner operating voltage,thus shifting the operation point of the lamp to lower power. However,applying said method is accompanied by several drawbacks. One of thedrawbacks is that the implementation of a lower burner voltage causesoverstressing of a ballast, which is electrically connected with thelamp, as a result of an increase of the input current to the electriccircuit. An increase of the current results generally in a shortening ofthe lifetime of one or more electric components, such as the ballast andthe lamp that are part of the operating electric circuit.

The invention has for its object to provide an electric circuit withwhich at least a conventional light output of the discharge lamp can begenerated at a relatively low power consumption without overstressingcomponents forming part of the electric circuit.

The invention provides for this purpose an electric circuit of the typestated in the preamble, characterized in that the electric circuit isprovided with a second inductor which is electrically connected inseries with the discharge vessel. By on the one hand applying arelatively low operating voltage across the electric circuit, and on theother hand limiting the current—which increases as a result of the lowoperating voltage—by applying the second inductor, a light intensity ofthe light radiation generated by the discharge lamp which issubstantially constant compared to the prior art can be obtained at arelatively low energy consumption. A higher light efficiency of thedischarge lamp will thus be obtained. One inference is that the lowerenergy consumption will result in less stress on the componentsincorporated in the electric circuit, which will increase the lifespanof the components. The second inductor is particularly suitable forapplication in electric circuits in which the resistance value of thefirst inductor (the ballast) is too low to substantially fullycompensate the increase in current resulting from the lower operatingvoltage. Owing to the substantially full compensation effect, causing anincrease of the current in the electric circuit due to the decrease ofthe operating voltage to be compensated by a (substantially equallylarge) lowering of the current by the second inductor, the current willbe substantially equal to the current in a prior art electric circuit.It will be apparent that the second inductor can also be replaced byanother type of electric component with a substantially comparablefunctionality, i.e. of reducing the current in the electric circuit.Examples of such other components are a heat-sensitive resistor, such asa PTC-resistor, and a light-sensitive resistor.

The discharge lamp is preferably formed by a high-pressure dischargelamp, which in particular is provided with sodium. However, in additionto applying a discharge vessel in which a relatively high pressureprevails, it is also possible to apply a discharge vessel in which arelatively low pressure is present, such as for instance a low-pressuredischarge lamp, which in particular is provided with sodium. Such a lampis also referred to as LPS lamp. In addition to sodium lamps it is alsopossible to apply High-Pressure Mercury Vapour Lamps in an electriccircuit according to the invention.

In a preferred embodiment the second inductor has an impedance ofbetween 2 Ω and 10 Ω, preferably 4 Ω, when a discharge lamp of 250 Wattsis applied. The optimal value of the second inductor depends among otherthings on the nature and technical properties of the componentsincorporated in the electric circuit, including the power to beprocessed by the lamp.

In another preferred embodiment the discharge lamp is provided with asecond condenser, which second condenser is connected in parallel withthe second inductor and is connected in series with the dischargevessel. Test results show that the inclusion of a second condenser inthe discharge lamp stimulates the ignition of the discharge vessel. Inaddition, the second condenser has a stabilizing effect on theelectrical circuit in the operative mode, whereby optimal functioning ofthe electric circuit can be achieved. The capacitance of the secondcondenser preferably lies between 5 nF and 15 nF, and is preferably 10nF. As already stated in the foregoing, the optimal value of thecapacitance of the second condenser depends among other things on thenature and properties of other components incorporated in the electriccircuit.

The invention also provides an electric component module for use in suchan electric circuit, in particular as an add-on device to the lamp. Theelectric component module is preferably provided with a plug forreleasable coupling of the component module to the first condenser, asocket for releasable coupling of the component module to the dischargelamp, and at least one electric component electrically connected to theplug and the socket. After coupling of the component module to thecondenser and the discharge lamp, the electric component arranged in thecomponent module is consequently incorporated in the electric circuit.Application of the component module in the electric circuit gives thecircuit a certain adaptive capability. A suitable component module canbe built into the electric circuit subject to the requirements set forthe electric circuit. Owing to the releasable coupling between thecomponent module and other electric components it is possible to replacethe component module in a simple and not very time-consuming manner inthe case of a malfunction one or more of the (electric) componentsforming part of the component module. The presence of a component moduletherefore increases the accessibility of the electrical componentsarranged in the component module. Another advantage is that existingfittings with built-in choke can be modified in a relatively simplemanner such that they meet the requirements of an electric circuit forigniting a discharge lamp according to the present invention. Theelectric component serves particularly to reduce the current runningthrough the electric circuit.

In a preferred embodiment the electric component is formed by the secondinductor. As already stated above, another type of electric componentwith a substantially comparable functionality, i.e. of reducing thecurrent, can also be applied instead of the second inductor. An exampleof such another type of component is for instance a thermoresistor,preferably a PTC-resistor, or a light-sensitive resistor. In aparticular, preferred embodiment the electric component is formed by thesecond inductor and a second condenser electrically connected inparallel with the second inductor.

The invention further provides a discharge lamp for use in an electriccircuit as described above. The discharge lamp is preferably providedwith the second inductor which is electrically connected in series withthe discharge vessel. Since the inductor reduces the current,incorporation of the discharge lamp in the electric circuit will—at arelatively low operating voltage—generally result in a relatively lowenergy consumption at an at least practically constant light output. Alower current in the electric circuit will generally result in a lowerstress on the components incorporated in the electric circuit, whichenhances the lifespan of the components.

The invention will be elucidated on the basis of non-limitativeembodiments shown in the following Figures. Herein:

FIG. 1 shows an electric circuit diagram corresponding with a firstpreferred embodiment of the invention,

FIG. 2 shows an electric circuit diagram corresponding with a secondpreferred embodiment of the invention, and

FIG. 3 shows a discharge lamp provided with an electric component moduleaccording to the invention.

FIG. 1 shows an electric circuit diagram 1 corresponding with a firstpreferred embodiment of the invention. Diagram 1 comprises analternating voltage source 2, a condenser 3 electrically connected tothe alternating voltage source 2, a first inductor 4 and an igniter 5.First inductor 4 and igniter 5 form a series chain 6, which series chain6 is electrically connected in parallel with the alternating voltagesource 2 relative to condenser 3. Diagram 1 is also provided with adischarge lamp 7 which is included in the diagram in parallel connectionwith igniter 5. Discharge lamp 7 is provided with a lamp cap 8, adischarge vessel 9 electrically connected to lamp cap 8, and a secondinductor 10 electrically connected in series with discharge vessel 9.For protection purposes the discharge vessel 9 and second inductor 10are mounted in an outer bulb 11 connected to lamp cap 8. Advantages ofthe present preferred embodiment have already been described above.

FIG. 2 shows an electric circuit diagram 12 corresponding to a secondpreferred embodiment of the invention. Diagram 12 is practicallyidentical to the electric circuit diagram shown in FIG. 1, with thedifference that a different preferred embodiment of a discharge lamp 13is included in diagram 12. Discharge lamp 13 comprises a lamp cap 14, adischarge vessel 15 electrically connected to lamp cap 14 and a parallelcircuit of a second condenser 16 and a second inductor 17 electricallyconnected in series with discharge vessel 15. The presence of the secondcondenser 16 stimulates the ignition of discharge vessel 15. Inaddition, condenser 16 has in particular a stabilizing effect onelectrical circuit 12.

FIG. 3 shows a discharge lamp 20 provided with an electric componentmodule 21 according to the invention. Discharge lamp 20 is provided witha lamp cap 22, a switching segment 23 connected to lamp cap 22 and anouter bulb 24 connected to switching segment 23. Component module 21 isprovided with a socket 25, which socket 25 is adapted for releasableelectrical coupling to a plug 26 forming part of switching segment 23.Incorporated in component module 21 is a parallel circuit of a condenser27 and an inductor 28, which parallel circuit is electrically connectedto socket 25. In the outer bulb is arranged a discharge vessel 29 whichon one side is electrically connected to lamp cap 22 and on an oppositeside is also electrically connected to lamp cap 22 via component module21. In the case of a malfunction of condenser 27 and/or inductor 28 thecomponent module 21 can be disconnected from switching segment 23 andthen replaced by a properly functioning component module. The couplingof component module 21 to switching segment 23 results in asubstantially uninterrupted circuit. The configuration shown in FIG. 3is thus constructed such that the parallel circuit is connected inseries with discharge vessel 29. In addition to the component module 21shown, component modules can also be envisaged which are provided withother electric components and/or a different relative orientation of thecomponents. It will be apparent that a component module can also bepositioned between a discharge lamp and an electric circuit, in whichcase the (existing) discharge lamps and electric circuits do not have tobe replaced by new constructions. Positioning of the adaptive componentmodule between the discharge lamp and the circuit is sufficient tocreate an electric circuit according to the invention.

1. An electric circuit for igniting a discharge lamp, at least one firstcondenser electrically connected to a voltage source, a series chain,electrically connected in parallel with the first condenser, of at leastone ignition and at least one first inductor, the discharge lampelectrically being connected in parallel with the ignition and beingprovided with a discharge vessel, and a module electrically connectedbetween discharge vessel and the at least one ignition, the modulecomprising a parallel connection of a second condenser electricallyconnected in parallel with a second inductor, the parallel connectionbeing electrically connected in series between the discharge vessel andthe at least one ignition.
 2. The electric circuit as claimed in claim1, wherein the discharge lamp is formed by a high-pressure dischargelamp.
 3. The electric circuit as claimed in claim 1, wherein thedischarge vessel is provided with sodium.
 4. The electric circuit asclaimed in claim 1, wherein the second inductor has an impedance ofbetween 2 Ω and 10 Ω.
 5. The electric circuit as claimed in claim 1,wherein the second inductor is incorporated in the discharge lamp. 6.The electric circuit as claimed in claim 1, wherein capacitance of thesecond condenser lies between 5 nF and 15 nF.
 7. The electric circuit ofclaim 1, wherein the module further comprises: a plug for releasablecoupling of the module to the first condenser; and a socket forreleasable coupling of the module to the discharge lamp.
 8. A lampsystem comprising: a discharge vessel; an igniter electrically connectedbetween the discharge vessel and a voltage source; a first condenserelectrically connected in parallel with the voltage source and a seriesconnection of the igniter and a first inductor; and a moduleelectrically connected between discharge vessel and the igniter; themodule including: a plug releasably coupling the module to the voltagesource; a socket for releasably coupling the module to the dischargevessel, and a parallel connection of a second condenser and a secondinductor, the parallel connection being electrically connected in seriesbetween the plug and the socket.